Well, it has a couple of limitations:
1. it only works from outside of the avast NT service (e.g. in a non-scheduled on-demand scan), not inside the service (i.e. on-access and scheduled on-demand) - unfortunately, this is a limitation of the messenger engine - it just doesn't seem to be working in a context of system service...
2. you must be logged on to messenger [passport] (avast doesn't log you on)
3. specify the buddy name to send the message to in the form of this e-mail address (not his nick) -- like gwb@whitehouse.gov instead of God Wannabe ...
Hope this helps,
Vlk